Yes, BIY mag. G3 style feed lips won't work due to length of the 45 WM cartridge; too much side-side wiggle. Working more toward VZ's pistol-style feed lips that feeds only from the middle and go further down on the mag. Size of my BIY follower is making the fitment challenging.

my piston to smooth tube fit is VERY good at sealing. Thus very efficient. I have not vented the sides of the gas tube yet, I have a hole in the top that will hold the front sight post that is empty and bleeding pressure for me right now.

OK I've been dinking around with my build for the past week. EVERYTHING IS WORKING... *EXCEPT* for the magazine. The feed lips are fine, I think. What the problem is, apparently, is that the cases are getting pinched at the base, and they are not moving in reaction to the upward spring pressure. It looks like they are too wide for the 1"x2" tubing. I have modified my homebuilt follower to try to compensate and it simply isn't enough.

It appears upon closer inspection that the tubing isn't a true parallel rectangle, but rather a football shape where the middle is wider than the ends. The inner width should be just over 7/8" wide, and the rear (where the base of the cartridges need to feed!) is less than 7/8".

Therefore, I need to find a way to bend the metal to make that inner width somewhat wider. I wonder if it would be as easy as sticking in a 7/8" bar stock and hammering the crap out it or pressing it down with the press? All of the tubing is like this... the corners are rounded just enough that the inner diameter isn't consistent.

I am going to see if I can mock-up one of these busted G3 mags to verify this is hte problem. Maybe it will be easier to modify a G3 mag after all?

could you weld up the ends and fill it with water and freeze it or maybe fill a plastic bag inside is and freeze it with the ends pluged some how? or possably hydro forming it?? just thinking out loud here. or maybe some gun powder and a fuse to blow it out LOL. likely all those meathods will just make it worse in the middle. milling a bar and pressing it through might be the best way possably adding some heat as you go.

I mocked up an aluminum G3 mag and it fed flawlessly! I used a 3/4" square aluminim rod to take up the space in the front so the spring wouldn't pop out, and my follower and the 45 WM dummies all fed fine! Looking more closely at the inside of the G3 mags, you can tell there is plenty of room inside to keep the rounds from hanging up.

I just happened to have some 3/4" and 1/8" stock laying around and I was able to hammer the inside of the mag out some. It is closer to where it needs to be, and does feed better. That implies I'm on the right track. I have some 1" stock that I am going to cut down and use for a mandrel to see if I can't get some real pressure from my 12-ton press to do the job. I may also file the inside some just to smooth things up after I'm done pressing it. Can't say for sure but it SEEMS to need a bit of polishing up on the inside.

Also, I made the body bent inward on the first 1" of the magazine to more closely imitate a pistol magazine that feeds only from the middle. The follower I have is too wide for that design, and the follwer in the pistol mag is actually only 3/4 as wide as the magazine, so that it can feed all the way up. I need to cut this follower down or make a new one to get those last few rounds to feed.

The rounds are still hanging ever so slightly in the mag and the follwer issue is making it difficult to isolate whether I need to cut more inside or thin the follower.

Progress is slow but steady. At least the bullpup linkage is working. Still need to snap some pics of it.

Here's your update - I'm almost fully recovered from a respiratory infection (still on meds) and finally feeling well enough to get out in the shop again.

I machined a mandrel out of some steel stock I ordered from speedy metals. The mandrel is just thick enough to widen the inside diameter. I used my press to drive the mandrel through the tube... plenty of grease. I rounded the front edges and made it slightly shorter front-to-back. It looks kind of like a small log splitting wedge.

IT WORKS! The rounds no longer bind up like they used to in the thinner magazine. So my observation was correct. The I.D. is about .900" at the back where the base of the rounds feed.

Also, I spent some time while I was sick measuring my double-stack pistol magazines. All have one thing in common - a 15 degree taper on both sides that is approximately 2 rounds long, and a drastic inward taper of some sort at the top of the lip. I chose to imitate the closest one (.45 ACP) so I tapered the sides 1.1" down, and bent the lips about 30 degrees on the top.

I had to cut my custom follower for the taper as it was built more like an AR follower - so now the sides are thinned and tapered to match the magazine taper, more like a pistol follower.

It feeds by hand, AND it feeds in the gun with no binding in the magazine. Happy Days

I still ran into some issues - fit and finish are still a bugger. I need to figure out how wide to make the ejector. I think it is too small as the rounds don't always eject. I think I can hit it with a weld bead and be OK.

The magazine's new shape is slightly tight in the magazine well I made, so I am going to have to find the sticky spots and sand them down in the magwell.

I also identified excessive hammer hump - ground that down and that made a world of difference!

There is still some friction with the bolt carrier and I think my center support is too high, which appears to be striking the bolt and interrupting the feed process JUST ENOUGH to cause some feed failures. I may have to trim the top down and machine away about 1/32" off of the top like I've seen on some factory models.

I am trying to develop this in such a way that I can imitate the build of the magazine so that the 10th magazine is identical to the 1st. That makes it easier for others to imitate!

The wife is probably going to keep me busy this weekend with the yard and garden, but I hope to get some work done tomorrow evening when she's off at work

My problem is in the magazine, I got it back from the guy who was going to bead park and gunkote it. He did none of these but he did run 200+ rounds through it. The mag is my problem, I am simply having feed problems after 2-3 rounds. I think I can work it out but I would like pics of your mag please